DALLAS Thousands of residents were without power and hundreds of flights canceled on Wednesday as authorities surveyed the damage a day after up to a dozen tornadoes struck the densely populated Dallas-Fort Worth area of Texas.

Hundreds of homes and businesses sustained significant damage in the outbreak that brought hail, high winds, and rain as it skipped through the area, tossing tractor-trailer trucks into the air and injuring at least 17 people.

Many of the 6.3 million area residents were forced to scramble for safety as the storm bore down during the early afternoon, when schools and workplaces were open in the fourth most populous U.S. metropolitan area.

The early warning for the storm - the Dallas-Fort Worth International Airport was tracking the storm for more than an hour before it reached there - enabled people to get to safety, officials said.

About 22,000 homes and businesses remained without power on Wednesday morning from Texas to Louisiana, Mississippi and Oklahoma.

Some 420 American Airlines and American Eagle flights in and out of Dallas-Fort Worth International Airport had been canceled Wednesday, said Tim Smith, a company spokesman. There were 66 American planes and 26 American Eagle planes out of service, Smith said.

About 1,400 people slept in airport terminals Tuesday night after the storms and an as yet undetermined number of passengers stranded by canceled flights were directed to area hotels, airport spokesman David Magana said.

A return to normal for the airport "will be measured in days, not hours," Magana said.

About 400 flights were canceled Tuesday at the airport, the eighth busiest in the world, and 40 incoming flights diverted. At the height of the storm, passengers were herded away from windows and into stairwells and restrooms, Magana said.

The tornadoes left "three major pockets of damage" in the Lancaster area south of Dallas, the Kennedale-Arlington area and in Forney, said Jud Ladd, chief of operational services at the weather service regional headquarters in Fort Worth.

Authorities were amazed no one was killed given the intensity of the storm, the number of tornadoes and the population density of the area.

SOME INJURIES, NO DEATHS

"The fortunate thing about it is there were some injuries, but no deaths we are aware of at this point," Ladd said Wednesday morning.

It is not uncommon for the Dallas-Fort Worth area to be struck by tornadoes, but "to have storms that do this kind of damage" has probably happened five or six times since the 1950s, Ladd said.

As of Tuesday night, 10 people had been reported injured in the Lancaster area, two severely, and seven in Arlington, one critically, police said.

One tornado lifted trucks like toys in the Flying J Truck Plaza in Dallas, said truck driver Michael Glennon, who caught the destruction on his video camera as debris swirled through the air.

Sixth-grader Hailey Pellerin said she and other students had just started lunch when teachers quickly herded students back to their classrooms in their southwest Arlington elementary school.

"We had to duck and cover for two hours," she said. The students were seated, lined up against a wall in their classrooms and covered their heads. "The power went out so it was dark and hot."

The tornado passed about 200 yards (180 meters) from the school, her father David Pellerin said.

On Tuesday evening, the storm system moved east into Oklahoma, Arkansas and Louisiana, the weather service said.

Heavy rain pelted the New Orleans area on Tuesday night and Wednesday, producing widespread street flooding, the weather service said. Forecasts called for up to 6 inches of rain through Wednesday evening with a flash flood watch.

The U.S. tornado season started early this year. Tornadoes have been blamed for 57 deaths so far in 2012 in the Midwest and South, raising concerns this year could be a repeat of 2011, the deadliest year in nearly a century for the unpredictable storms.

In 2011, there were 550 tornado deaths, including 316 lives lost on April 27 in five southern states, and a massive tornado that killed 161 people in Joplin, Missouri, on May 22.

Tuesday's tornadoes in Texas could prove more costly than a hailstorm nearly a year ago in the Dallas area that caused more than $100 million in insured losses. That April 15, 2011, storm was less damaging in terms of hail and winds.

Insurers have already lost as much as $2 billion during the 2012 tornado season, mostly from a record March 2 outbreak. That follows record-breaking losses of $26 billion during the 2011 tornado season.

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